In an orthotopic mouse xenograft model with murine bladder cancer MB49 cells, knockdown of Rab27b or its effector SYTL3 in MB49 and concurrent treatment with an exocytosis inhibitor GW4609 in MB49-bearing mice similarly enhanced the anti-tumor effects of intravesical BCG therapy, while increasing the amount of BCG evaluated via acid-fast bacillus staining. The gene discussed is RAB27B; the disease is urinary bladder cancer.